Different Types of Email Bounces

Email Bounces Types

When doing email marketing, some status codes will be returned in the log to inform whether the email is sent successfully, similar to the status code in the header when visiting a website , 404 means the page does not exist, etc. The status code 2.0.0 of the sent mail indicates successful delivery, and the soft Bounce and Hard Bounce status codes we often talk about are summarized as follows:

Bounce codeBounce typeDescription
5.0.0HardAddress does not exist
5.1.0HardOther address status
5.1.1HardBad destination mailbox address
5.1.2HardBad destination system address
5.1.3HardBad destination mailbox address syntax
5.1.4HardDestination mailbox address ambiguous
5.1.5HardDestination mailbox address valid
5.1.6HardMailbox has moved
5.1.7HardBad sender’s mailbox address syntax
5.1.8HardBad sender’s system address
5.2.0SoftOther or undefined mailbox status
5.2.1SoftMailbox disabled, not accepting messages
5.2.2SoftMailbox full
5.2.3HardMessage length exceeds administrative limit.
5.2.4HardMailing list expansion problem
5.3.0HardOther or undefined mail system status
5.3.1SoftMail system full
5.3.2HardSystem not accepting network messages
5.3.3HardSystem not capable of selected features
5.3.4HardMessage too big for system
5.4.0HardOther or undefined network or routing status
5.4.1HardNo answer from host
5.4.2HardBad connection
5.4.3HardRouting server failure
5.4.4HardUnable to route
5.4.5SoftNetwork congestion
5.4.6HardRouting loop detected
5.4.7HardDelivery time expired
5.5.0HardOther or undefined protocol status
5.5.1HardInvalid command
5.5.2HardSyntax error
5.5.3SoftToo many recipients
5.5.4HardInvalid command arguments
5.5.5HardWrong protocol version
5.6.0HardOther or undefined media error
5.6.1HardMedia not supported
5.6.2HardConversion required and prohibited
5.6.3HardConversion required but not supported
5.6.4HardConversion with loss performed
5.6.5HardConversion failed
5.7.0HardOther or undefined security status
5.7.1HardDelivery not authorized, message refused
5.7.2HardMailing list expansion prohibited
5.7.3HardSecurity conversion required but not possible
5.7.4HardSecurity features not supported
5.7.5HardCryptographic failure
5.7.6HardCryptographic algorithm not supported
5.7.7HardMessage integrity failure
9.1.1HardHard bounce with no bounce code found. It could be an invalid email or rejected email from your mail server (such as from a sending limit).
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